Slow speed weigh-in-motion system with flexure

ABSTRACT

In one embodiment, a weighing system includes a base, a platform structure movable with respect to the base, at least one flexure fixedly attached to the platform and the base, the at least one flexure configured to inhibit movement of the platform structure along a horizontal plane relative to the base, and a plurality of load cell assemblies, each of the plurality of load cell assemblies including an upper portion pivotably supported by the base through a first pivot assembly and a lower portion pivotably supporting the platform structure through a second pivot assembly, wherein an axis of rotation of the first pivot assembly is parallel to an axis of rotation of the second pivot assembly.

This is a continuation-in-part application of application Ser. No.14/176,190, filed Feb. 10, 2014, the entirety of which is incorporatedherein by reference.

TECHNICAL FIELD

This disclosure relates generally to weighing systems, and, inparticular, to scales for weighing heavy loads.

BACKGROUND

Vehicles operating on roadways are often weighed to determine the axleweight and the total weight of the vehicle. In some operations, theweight of the vehicle is important to ensure compliance with weightrestrictions on public roadways. Owners and operators of vehiclesexceeding maximum legal weights are subject to fines, and in the eventof an accident, can be subject to substantial financial liability foroperating a vehicle exceeding the maximum legal weight. It is thereforedesirable to weigh trucks and other vehicles which will be operating onpublic roadways.

One way vehicles are weighed is by driving the vehicle onto a staticscale that is large enough to accommodate the entire vehicle. While sucha scale is typically accurate to determine the load carried by thevehicle, such scales are very large and very expensive, and must becapable of accommodating and accurately measuring substantial weights.Furthermore, such scales do not enable determination of the weightcarried by each individual axle of the vehicle.

Another weighing system involves driving the vehicle onto a smallerscale sized to weigh each individual axle. Such scales typically requiredriving the axles onto the scale individually, and stopping to weigheach axle. As the vehicle stops and restarts, the load carried by thevehicle can shift, resulting in weight readings that are not accurate.Additionally, the suspension of the vehicle can shift during thestopping and restarting of the vehicle, further reducing the accuracy ofthe weight measurement.

Some vehicle scales, such as the axle scale 20 shown in FIG. 1, aredesigned to weigh each axle of the vehicle as the vehicle drives overthe scale 20 at a constant speed. Such scales typically include fourload cells (only two are shown in FIG. 1) 24, 26 positioned underneaththe scale, one located in each corner positioned inwardly from the outeredges of the weighing portion, also known as the active section 28. Asthe vehicle tires 32 pass over the active section of the scale, the loadcells 24, 26 are compressed, and generate a load signal representing theweight of the axle passing over the scale 20.

However, as the vehicle tires 32 first roll onto the active section 28,the downward force 36 from the vehicle is outside an area between theload cells 24, 26 located under the active section 28. A moment 40 istherefore generated, whereby the load cells 26 opposite the tires 32 areurged upwardly 38 while the load cells 24 nearest the tires 32 are urgeddownwardly 39. A moment is generated in the opposite direction as thewheels pass the load cells under the opposite side of the activesection. These moments affect the accuracy of the weight measurement,and make it more difficult to obtain a weight reading of the movingaxles.

Additionally, in a typical axle scale 20, the load cells 24, 26 aredesigned to measure a compression force generated by the additionalweight of the vehicle axle on the scale. The load cells 24, 26 supportthe platform of the active section 28 of the scale 20 from underneaththe platform, as shown in FIGS. 1 and 2. As the vehicle tires 32 rollonto the platform, the momentum of the wheels urges the platform in thehorizontal direction of movement of the vehicle, illustrated by arrow44. This movement generates a moment 48 about the support of the loadcells 24, 26, resulting in forward and downward movement of the activesection 28 relative to the support of the load cells 24, 26. Thedownward force 36 from of the weight of the load further supplements theforward and downward movement of the active section 28. This forward anddownward movement can result in inaccurate weighing of the vehicle.

In some scales, the platform is designed to abut against a stop locatedoutside the active section of the scale in order to arrest this forwardand downward movement, and the scale then settles back into the naturalposition. While such a solution is effective to stop the forwardmovement, it takes time for the platform to move against the stop andstabilize, increasing the time the axle must be on the scale to producea weight reading.

Installation of a vehicle scale is a time consuming, cumbersome, andexpensive process. Significant construction equipment is required toexcavate the scale site, install a frame, and cast concrete pads withinthe scale site. Furthermore, specialized tools and knowledge arerequired to install and calibrate the load cells and the moving parts ofthe scale at the site. If installation is not performed precisely, thescale readings can be subject to substantial errors.

Once installed, typical vehicle scales require routine maintenance toremove objects and debris that can pass through a gap 56 (FIG. 1)between the active section 28 and the surrounding area. Performing thismaintenance requires removal of the active section of the scale to cleanthe area underneath the platform. The active section of typical vehiclescales are difficult to remove, since the load cell, which is locatedunderneath the platform, must be decoupled from either the base or theplatform. Additionally, removal and replacement can sometimes requirerecalibration of the scale, which generally must be performed by atrained specialist.

A scale for heavy loads that has improved measurement accuracy istherefore desirable. Furthermore, it would be desirable to produce ascale for heavy loads that is simpler to install and maintain.

SUMMARY

In one embodiment a weighing system provides faster stabilization andimproved weighing accuracy of a moving load. The weighing system has abase, a platform structure movable with respect to the base andincluding a planar top surface defining a horizontal plane, at least oneflexure fixedly attached to the platform and the base, the at least oneflexure configured to inhibit movement of the platform structure alongthe horizontal plane relative to the base, and a plurality of load cellassemblies, each of the plurality of load cell assemblies including anupper portion pivotably supported by the base through a first pivotassembly and a lower portion pivotably supporting the platform structurethrough a second pivot assembly, each of the plurality of load cellassemblies positioned such that when the upper portion of each of theplurality of load cell assemblies is projected onto the plane and theplanar top surface is projected onto the plane, each of the projectedupper portions is located outwardly of the projected planar top surface,wherein an axis of rotation of the first pivot assembly is parallel toan axis of rotation of the second pivot assembly.

In one or more embodiments, the platform structure includes a frame witha first beam, and the at least one flexure is fixedly attached to thefirst beam.

In one or more embodiments, the frame includes a second beam spacedapart from the first beam, and the at least one flexure is fixedlyattached to the second beam.

In one or more embodiments, the platform includes at least one flexureopening, the at least one flexure is fixedly attached to the base by atleast one bolt, and the at least one bolt is accessible through theplanar top surface through the at least one flexure opening.

In one or more embodiments, the at least one flexure includes aplurality of flexures.

In one or more embodiments, each of the plurality of flexures ispositioned such that as a vehicle passes over the platform structureduring a weighing operation, each of a plurality of wheels of thevehicle passes directly above a respective one of the plurality offlexures.

In accordance with one embodiment, a method of providing a weighingapparatus includes forming a base having a scale opening, and aplurality of load cell openings opening laterally to the scale opening,providing a support member pair for each of the load cell openings,forming a platform structure, pivotably mounting a lower portion of eachof a plurality of load cell assemblies to the platform structure througha first pivot assembly, fixedly connecting at least one flexure to theplatform structure, supporting an upper portion of each of a pluralityof load cell assemblies with a respective one of the support memberpairs through a second pivot assembly, wherein an axis of rotation ofthe first pivot assembly is parallel to an axis of rotation of thesecond pivot assembly, and fixedly connecting the at least one flexureto the base after supporting the upper portion of each of the pluralityof load cell assemblies.

In accordance with one or more embodiments, fixedly connecting at leastone flexure to the platform structure includes fixedly connecting the atleast one flexure to a first beam of a frame of the platform structure.

In accordance with one or more embodiments, fixedly connecting at leastone flexure to the platform structure includes fixedly connecting the atleast one flexure to a second beam of the frame of the platformstructure, the second beam spaced apart from the first beam.

In accordance with one or more embodiments, fixedly connecting the atleast one flexure to the base includes inserting a bolt at leastpartially through the at least one flexure and into a bolt hole in thebase, accessing the bolt through a top surface of the platformstructure, and tightening the accessed bolt.

In accordance with one or more embodiments, fixedly connecting at leastone flexure to the platform structure includes positioning each of aplurality of flexures such that as a vehicle passes over the platformstructure during a weighing operation, each of a plurality of wheels ofthe vehicle passes directly above a respective one of the plurality offlexures, and fixedly connecting each of the positioned plurality offlexures to the platform structure.

In accordance with one or more embodiments, a method of weighing avehicle includes moving at least a portion of a vehicle onto a platformstructure including a planar top surface defining a horizontal plane bymovement of a portion of the vehicle past at least two of a plurality ofload cell assemblies and then onto a platform structure, wherein theplatform structure is supported by a plurality of load cell assembliesthrough a plurality of first load transfer areas, and each of theplurality of load cell assemblies is supported by a base through arespective one of a plurality of first load transfer areas, each of thefirst load transfer areas located farther from the horizontal plane thaneach of the second load transfer areas, inhibiting movement of theplatform structure along the horizontal plane using at least one flexurefixedly attached to the platform structure and the base, forcing each ofthe second load transfer areas from a neutral position directly awayfrom the horizontal plane by moving the at least a portion of thevehicle onto the platform structure, and determining a weight based uponsignals generated by the plurality of load cell assemblies.

In accordance with one or more embodiments, inhibiting movement of theplatform structure along the horizontal plane includes inhibitingmovement of the platform structure along the horizontal plane using atleast one flexure fixedly attached a first beam of a frame of theplatform structure.

In accordance with one or more embodiments, inhibiting movement of theplatform structure along the horizontal plane includes inhibitingmovement of the platform structure along the horizontal plane using atleast one flexure fixedly attached to a second beam of the frame of theplatform structure, the second beam spaced apart from the first beam.

In accordance with one or more embodiments, moving at least a portion ofa vehicle onto a platform structure includes moving each of a pluralityof wheels of the vehicle directly above a respective one of theplurality of flexures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side schematic cut away view of a tire on an active sectionof a prior art axle scale showing a tipping moment produced on theactive section.

FIG. 2 is a partial side schematic cut away view of a tire moving acrossan active section of a prior art axle scale showing a moment producedabout the supports of the active section.

FIG. 3 is a side perspective view of a prefabricated axle scale.

FIG. 4 is a top plan view of the base portion of the prefabricated axlescale of FIG. 3 showing the base frame located within the base portionand the platform structure removed for clarity.

FIG. 5 is a top plan view of the platform structure of the prefabricatedaxle scale of FIG. 3.

FIG. 6 is a partial side cross-sectional view through the connectingassembly of the axle scale of FIG. 3 showing the connecting plate, theload cell, and the saddle member.

FIG. 7 is a side perspective view of the connecting assembly of FIG. 6,with the base removed for clarity.

FIG. 8 is a front cross-sectional view of the connecting assembly ofFIG. 6.

FIG. 9 is a side view of the load cell assembly of the axle scale ofFIG. 3.

FIG. 10 is a schematic diagram of the load cells and controller of theprefabricated axle scale of FIG. 3.

FIG. 11 is a side schematic view of a tire moving across the axle scaleof FIG. 1.

FIG. 12 is a side schematic view of a tire moving onto the axle scale ofFIG. 1.

FIG. 13A is a graph showing the load cell readings for a vehicle axlepassing over a load cell assembly of the axle scale of FIG. 1.

FIG. 13B is a graph showing the load cell readings for a vehicle axlepassing over a load cell assembly of the axle scale of FIG. 1.

FIG. 14 is a process diagram of a method of operating an axle scale.

FIG. 15 is a process diagram of a method of manufacturing aprefabricated axle scale.

FIG. 16 is a process diagram of a method of installing a prefabricatedaxle scale.

FIG. 17 is a process diagram of a method of performing a maintenanceoperation on an axle scale.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of thedisclosure, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the disclosure is therebyintended. It is further understood that this disclosure includes anyalterations and modifications to the illustrated embodiments andincludes further applications of the principles of the disclosure aswould normally occur to one skilled in the art to which this disclosurepertains.

FIG. 3 illustrates a perspective view of a prefabricated vehicle axlescale 100. The axle scale 100 includes a base 104, a platform structure108, and a controller 110.

With further reference to FIG. 4, which shows the axle scale 100 withthe platform structure 108 removed, in the illustrated embodiment, thebase 104 is shaped substantially as a rectangular prism. In otherembodiments, however, the base has a different shape, for example atrapezoidal, rounded, or irregular shape. The base 104 includes a baseframe 112 and a concrete body 116 (shown in shadow in FIG. 4), whichdefines a generally flat upper surface 120 of the base 104.

The base frame 112 is surrounded by the concrete body 116 and defines ascale or platform opening 124. The base frame 112 is formed ofstructural steel, for example C-channel steel, webbed steel beams, orsteel plates, welded together in the shape of a rectangle having fourload cell openings 128 extending outwardly therefrom. Each load cellopening 128 opens laterally to the platform opening 124 and is coveredby a removable load cell cover 132, which is substantially flush withthe upper surface 120 of the concrete body 116. As will be described ingreater detail below, each load cell opening 128 includes a supportmember pair, which in the illustrated embodiment is provided by twosaddle members 136 affixed to the base frame 112, with one saddle member136 on each lateral side of the load cell openings 128.

The base 104 has four lift members 140 positioned symmetrically aboutthe vertical and horizontal axes of the base 104. Each of the liftmembers 140 is anchored in a well 142 in the concrete body 116 bysupport plates 143 embedded in the concrete body 116, and are accessedthrough a lift member covering plate 144 that is substantially coplanarwith the upper surface 120 of the concrete body 116. Each lift member140 includes an attachment member (not shown), for example one or morechain links, fixed in the well 142 to enable a lifting device, such as aforklift, a crane, or a backhoe, to attach to the lift members 140 witha chain or hook.

The base 104 further includes a cable conduit 148 embedded in theconcrete body 116 beneath the platform opening 124. In the illustratedembodiment, the cable conduit 148 is one inch diameter PVC and extendsalong the longitudinal axis of the base portion, though in otherembodiments other sizes and materials are used for the cable conduit 148and the cable conduit 148 runs in a different orientation within theconcrete body 116. The cable conduit 148 is configured to carry wiresthat connect components within the platform structure 108, such as loadcells, to the controller 110. Two flexure bases 149 including aplurality of bolt holes are provided in the base 104. The bolts holesare substantially centered within the platform opening 124.

The base 104 also includes a drain aperture 152 (shown in shadow in FIG.4) extending through the concrete body 116 at one end of the platformopening 124. The drain aperture 152 is located at or below a bottomsurface of the platform opening 124 such that water and other liquidsdrain out of the platform opening 124 through the drain aperture 152.

Referring now to FIG. 5, which is a top plan view of the platformstructure 108, with continuing reference to FIG. 3, the platformstructure 108 includes a platform frame 160 surrounding an innerconcrete body 164. The platform frame 160 includes steel beams 168, 170,and 172, which, in one embodiment are W5×19 steel beams, weldedtogether. Two flexures 177 extend between the lower surfaces of thebeams 168. In some embodiments a single flexure is provided while inother embodiments more than two are provided. In some embodiments, theflexures are positioned such that wheels of a vehicle pass directlyabove the flexures as the vehicle passes over the platform during aweighing operation. The flexures 177 are stainless steel plates of about20-60 thousandths of an inch, and preferably about 30 thousandths of aninch. In one embodiment, the flexures 177 are about 7.5 inches in widthand formed from a form of steel such as stainless steel, carbon steel,etc.

Two flexure cover plates 189 cover flexure openings in the platformstructure 108 and are removable to provide access to the flexures fromabove the platform structure 108 so that bolts 179 can be used to boltthe flexures 177 to the flexure bases 149. When fixedly connected toboth the platform structure 108 and the flexure bases 149, the flexures177 are preferably substantially planar and parallel to a horizontalplanar top surface 180 of the platform structure 108. To reduce anydeflection of the flexures 177 out of this configuration, shims may bepositioned as necessary between the flexures 177 and the flexure bases149.

The platform frame 160 defines a rectangular shape and is sized to fitwithin the platform opening 124 of the base 104 with a minimalclearance, which, in one embodiment, is approximately ½ inch on eachside of the platform frame 160. The long steel beams 168 define outeredges 176, which are substantially aligned with the long edges of theplatform opening 124 when the platform structure 108 is installed in theplatform opening 124.

The top surface of the inner concrete body 164, along with the topsurface of the steel beams 168, 170, 172 define a horizontal planar topsurface 180 of the platform structure 108, which is substantiallycoplanar with the upper surface 120 of the base 104. An opening 184 isdefined in the inner concrete body 164 to enable maintenance andconnection of wires within the platform structure 108. In someembodiments, an electronic module (not shown) is located within theopening 184 to facilitate connection of the wires in the platformstructure 108. The opening 184 is covered by an opening cover plate 188(FIG. 1), which has a surface that is substantially coplanar with thetop surface 180 of the platform structure 108.

Four anchor points 192 are embedded in wells 194 in the inner concretebody 164 and are attached to the outer steel beams 168, 170 at eachinside corner of the outer steel beams 168, 170. The anchor points 192are functionally the same as the lift members 140 of the base 104, andeach anchor point 192 is accessed through an anchor plate 196 configuredto be flush with the top surface 180 of the platform structure 108. Eachanchor point 192 further includes an attachment member (not shown), forexample one or more chain links, fixed in the anchor point 192 to enablea lifting device, such as a forklift, a crane, or a backhoe, to attachto the anchor point 192 with a chain or hook.

The platform structure 108 is supported by four connecting assemblies200, which are illustrated in FIGS. 6-8, each of which is positioned inone of the load cell openings 128 when assembled. The connectingassemblies 200 each include two connecting plates 202, a load cellassembly 204, a load pin 212, a fulcrum pin 216, and the pair of saddlemembers 136. Each pair of connecting plates 202 supports the load cellassembly 204. Each of the connecting plates 202 has a first end shapedto fit vertically between the flanges 169 of steel beam 168, and thefirst end is welded securely to the flanges 169 and the web of the steelbeam 168. Opposite the first end, the connecting plates 202 include loadpin apertures 208, which support the ends of the load pin 212.

As is illustrated in FIGS. 6-9, the load pin 212 extends between theconnecting plates 202 through a load pin opening 214 in a lower portion218 of the load cell assembly 204. The load pin opening 214 ischamfered, having a lesser diameter at the top than at the bottom of theload pin opening 214. The load pin 212 thus rests at the top of the loadpin opening 214, against a bearing surface 219 in the load cell assembly204. The fulcrum pin 216 extends between the saddle members 136 througha fulcrum pin opening 220 in an upper portion 222 of the load cellassembly 204, above the load pin 212. The fulcrum pin opening 220 isalso chamfered, having a lesser diameter at the bottom than at the topof the fulcrum pin opening 220. The fulcrum pin 216 thus rests at thebottom of the fulcrum pin opening 220, against a bearing surface 223.Since the load pin 212 and the fulcrum pin 216 are supported against thebearing surfaces 219, 223, respectively, the load cell assembly 204 ispivotable relative to the platform structure 108 and the base 104 and,in particular, the load pin 212 rotates about the fulcrum pin 216. Eachof the load pin 212 and the fulcrum pin 216 is operably connected to astrain sensing component 224 of the load cell assembly 204. In oneembodiment, the load cell assembly 204 is a model T95 shear beam loadcell sold by Thames-Side Sensors Limited, though other desired load cellassemblies are used in other embodiments.

The fulcrum pin 216 extends through a fulcrum pin opening 232 in theconnecting plates 202 without contacting either of the connecting plates202. The saddle members 136 include saddle grooves 236 having a tapered“U”-shape with upwardly opening mouth portions 238 and closed lowerportions 240. In some embodiments, one or more of the saddle grooves 236have a “V”-shape or a trapezoidal shape, and in some embodiments thesaddle grooves 236 of the saddle members 136 are shaped differently fromthe opposing saddle member 136. As is best shown in FIGS. 6 and 7, theends of the fulcrum pin 216 rest in the closed lower portion 240 of thesaddle groove 236 of the saddle member 136.

FIG. 10 is a schematic diagram of the controller 110 and the componentscommunicating with the controller 110 in the axle scale 100. Operationand control of the various components and functions of the axle scale100 are performed with the aid of the controller 110. The controller 110is implemented with a general or specialized programmable processor 264that executes programmed instructions. In some embodiments, thecontroller includes more than one general or specialized programmableprocessor. The instructions and data required to perform the programmedfunctions are stored in a memory unit 268 associated with the controller110. The processor 264, memory 268, and interface circuitry configurethe controller 110 to perform the functions described above and theprocesses described below. These components can be provided on a printedcircuit card or provided as a circuit in an application specificintegrated circuit (ASIC). Each of the circuits can be implemented witha separate processor or multiple circuits can be implemented on the sameprocessor. Alternatively, the circuits can be implemented with discretecomponents or circuits provided in VLSI circuits. Also, the circuitsdescribed herein can be implemented with a combination of processors,ASICs, discrete components, or VLSI circuits.

The processor 264 is operably connected to and configured to obtain theload signals generated by the load cells 204, and the load signalsobtained by the processor 264 are stored in the memory 268 of thecontroller 110. The controller 110 further includes an input/outputdevice 272 operably connected to the processor 264 to enable a user toinput parameters and activate operating algorithms for the processor264, and to enable the controller 110 to display information to the userof the axle scale 100. The processor 264 is also operably connected to aprinter 276, and is configured to transmit electronic signals to theprinter 276 to operate the printer to print a receipt indicating theaxle loads determined by the processor 264. In the illustratedembodiment, the processor 264, the memory 268, the input/output unit272, and the printer 276 are all contained within a common housing ofthe controller 110, which is installed proximate to the base 104 andplatform structure 108 of the axle scale 100. In other embodiments, oneor more of the control components, for example the printer 276, arelocated remote from the common housing of the controller 110.

To operate the axle scale 100, a user activates a command on theinput/output unit 272 of the controller 110 of the axle scale 100indicating that a vehicle is to be driven over the scale 100. In someembodiments, the user activates the command remotely via, for example,Wi-Fi, Bluetooth, infrared, or another desired wireless transmission. Inyet another embodiment, the controller 110 is configured toautomatically register the presence of the vehicle and autonomouslyactivates the command using, for example, a radio frequencyidentification (“RFID”) tag on the vehicle. In further embodiments, theready command is automatically activated by the controller 110 upondetection of a predetermined weight on the scale 100, indicating that aweighing operation is commencing.

The user then drives the vehicle over the axle scale 100. In oneembodiment, the vehicle is driven over the scale at a constant speed ofapproximately 2-5 miles per hour. As illustrated in FIGS. 6, 9, 11, and12, as the vehicle rolls over the axle scale 100, the wheels 32 of eachaxle first pass onto the upper surface 120 of the base 104. The wheelsof the axle subsequently pass onto the top surface 180 of the platformstructure 108. In one embodiment, the base 104 of the axle scale 100 issized such that, for a semi-truck having tandem axles, the wheels ofboth tandem axles are on the upper surface 120 of the base 104 prior tothe wheels of the leading axle moving onto the top surface 180 of theplatform structure 108. This provides a stable base for the wheels ofthe tandem axle that is not on the platform structure 108 while theother axle is being weighed by the platform structure 108.

As the wheels pass onto the top surface 180 of the platform structure108, the flexures 177 inhibit movement of the platform structure 108within the opening 124. Specifically, the half of the flexure 177 whichis subjected to tension along the horizontal plane resist movement alongthe horizontal plane. Accordingly, in some embodiments wherein vehiclesmove only in a single direction, the flexures are connected to theplatform structure only at a location proximate the location at whichthe vehicle moves onto the platform.

Additionally, the force 280 from the wheels 32 acts downwardly on thesteel beams 168, 170, 172 and the inner concrete body 164. The downwardforce from the steel beams 168 is transferred to the connecting plates202, which subsequently apply downward load force components 284 to theload pins 212 at a lower load transfer area 286. In response to thedownward load force components 284, the fulcrum pins 216 are subjectedto an upward reaction force 288 from the saddle groove 236, which isalso imparted on the load cell assembly 204 at upper load transfer area290.

The load cell assembly 204 is configured to periodically generate anelectronic signal indicative of the tension force between the load pin212 and the fulcrum pin 216 as measured by the strain sensing component224. In one embodiment, the load cell assembly 204 is configured togenerate the electronic signal at 100 Hz, though in other embodimentsalternative sampling rates are used. The processor 264 receives theelectronic signals from the load cell assemblies 204 and stores the datain memory 268.

FIG. 13A illustrates a graph 320 of load values, 324, or the forcemeasured by a load cell, over time for a vehicle driving over the axlescale 100. Each load value 324 on the graph 320 represents a readingfrom the load cells, or an average of load cell readings over apredetermined time period. As an axle begins moving onto the scale, theload values 324 increase until a minimum axle load 328 is reached. Anaxle window 336 begins at the time when the load values 324 reach theminimum axle load 328. The processor 264 thus begins storing the loadvalues 324 in the memory 268 as being associated with the axle window336, shown in further detail in FIG. 13B. The load values 324 increaseto a “plateau” while the wheels of the axle are on the scale, and thendecrease as the wheels of the axle move off the scale. The flexures 177reduce the time needed for the plateau to be realized. The flatness atthe top of the plateau depends on numerous variables and parameters.Once the load values 324 decrease below a value representing apredetermined hysteresis value 332 subtracted from the minimum axle load328, the processor 264 ceases to record the load values 324 in the axlewindow 336. In some embodiments, the processor is configured to generatean error if the number of load values in the axle window is below apredetermined number, indicating that the vehicle was driven over theaxle scale too fast.

The processor 264 is configured to identify a predetermined windowoffset 344, which, in one embodiment, is 30% of the load values 324 inthe axle window 336, and a stabilized window 348, which includes apredetermined number or percentage of load values 324 immediatelyfollowing the end of the window offset 344. In one embodiment, thestabilized window includes 40% of the load values 324 in the axle window336. The load values 324 in the window offset 344 and the load values324 occurring after the stabilized window 348 are discarded, leavingonly the stabilized load values 352 within the stabilized window 348.

Once stabilized load values 352 are available, the processor determinesa final load value by averaging the stabilized load values 352 from thestabilized window 348. The final load value for the axle is then storedin the memory 268.

Referring back to FIG. 13A, the processor 264 continues to obtain theload readings 324 from the load cell assemblies 204 for each individualaxle passing over the platform structure 108, calculating the final axleload for each axle of the vehicle. Once the processor 264 identifiesthat the vehicle has completely passed over the platform structure 108,by, for example identifying that the load values 324 do not exceed theminimum axle load 328 for a predetermined idle time 356, the processor264 sums the calculated axle loads and displays the total vehicle loadand axle loads on the input/output unit 272 and/or operates the printer276 to print a receipt indicating the total vehicle weight and theindividual axle loads.

The configuration of FIGS. 3-10 provides substantial benefits over knownaxle scales. For example, the load cells 204 are pivotable relative tothe platform structure 108 and the base 104, as shown in FIGS. 6 and 11.Lateral motion 292 imparted on the platform structure 108 of the scale100 is transmitted through the connecting plates 202 to the load pin212. The load pin 212 is configured to move in an arcuate path 296centered about the fulcrum pin 216. Since the load pin 212 is positionedbelow the fulcrum pin 216, an upward motion of the load pin 212 isrequired in order for the load pin 212 to move about the fulcrum pin 216along the arcuate path 296. The load pins 212 are fixed to the platformstructure 108, and therefore the platform structure 108 moves in anarcuate path 300 having a radius equal to the radius of the arcuate path296 of the load pins 212. As a result, an upward motion of the platformstructure 108 is necessary for the scale portion to move horizontally inresponse to lateral forces 292 produced by a load, for example vehicletire 32, moving across the top surface 180 of the platform structure108. This upward motion is opposed by the downward load force 280 fromthe weight of the load on the platform structure 108, which istransferred through the connecting plates 202 to the load pins 212 asdownward force components 284. Consequently, in contrast to the priorart axle scale 20 depicted in FIG. 2, the platform structure 108 of theaxle scale 100 acts as a self-stabilizing pendulum, as the load force280 dampens lateral motion 292 of the platform structure 108 with eachpendulum stroke of the platform structure 108. The flexures 177 furtherdampen lateral motion.

Additionally, since the load cells 204, if projected onto a planeparallel to the plane defined by the top surface 180 of the platformstructure 108, are positioned horizontally displaced from the topsurface 80 so as to be outside the area of the top surface 180 projectedonto the same plane, an object on the platform structure 108, forexample vehicle tire 32 (FIG. 12), will always be inside an area boundedby the load cell assemblies 204. As a result, in contrast to the priorart axle scale 20 depicted in FIG. 1, no tipping moment is generatedabout the load cell assemblies 204 when the vehicle tire 32 passes fromthe upper surface 120 of the base 104 to the top surface 180 of theplatform structure 108. All load cell assemblies 204, therefore, willonly be subject to load force components 284 directed downwardly, whichresults in less jitter in the load readings and quicker stabilization ofthe load readings to the stabilized load zone 348 (FIG. 13B).

A process diagram of a method 400 of weighing a vehicle is depicted inFIG. 14. The process refers to a processor, such as processor 264,executing programmed instructions stored in a memory associated with theprocessor to operate the components in an axle scale, such as axle scale100, to implement the method 400.

The process begins with the processor receiving an input indicating thata weighing operation is commencing (block 404). In one embodiment, theinput is indicative only that a vehicle is about to be driven over or isbeing driven on the scale. In another embodiment, the input isassociated with a particular vehicle, and can correspond to a pre-loadweight or a post-loading weight to enable determination of net weight ofthe load in the vehicle. In some embodiments, the controller isconfigured to receive an indication that a weighing operation iscommencing by receiving signals from the load cells indicating that avehicle is moving onto the scale, for example by identifying that theload on the load cells exceeds a minimum axle load. In anotherembodiment, the input is received directly at an input/output unit ofthe controller, while in other embodiments the input is transmittedwirelessly by a remote using Wi-Fi, Bluetooth, or infrared, orautomatically received from a wireless device, for example an RFID tagon the vehicle.

The vehicle is then driven over the scale at a constant or substantiallyconstant speed. In some embodiments, the processor is connected to analarm light or speaker to produce a visual or audible warning to thedriver that the vehicle exceeds a maximum speed at which the scale canobtain an accurate reading. As the vehicle drives over the scale, theload cells are forced away from their neutral position and thecontroller obtains electronic signals from the load cells correspondingto the force components of the load on each individual load cell andstores the readings in the memory (block 408). In one embodiment, theprocessor sends commands to the load cells to activate the load cells togenerate the load signals, while in another embodiment the load cellsare configured to transmit the load signals autonomously in response toa load being detected or the load cells are configured to constantlytransmit load signals. In yet another embodiment, the load cellscontinuously generate load signals, and the processor retrieves the loadsignals as needed. The load readings from the load cells increaserapidly as the tires from the axle move onto the scale. As the tirescontinue to roll across the scale, the load readings stabilize at aplateau, or stabilized load value, which is representative of the weightof the axle on the scale. The controller determines the stabilized loadvalue of the load cell readings (block 412) from each of the load cells.As discussed above, the stabilized load value is determined byidentifying the load cell readings falling within a stabilized window,which is a predetermined percentage of the load cell readings occurringin an axle window after a window offset is identified. The stabilizedload values are then averaged to calculate the total axle load, which isstored in the memory (block 416).

If there are additional axles to pass over the scale (block 420), thenthe process continues at block 408. If all the axles have passed overthe scale, then the processor proceeds to calculate the total vehicleload (block 424) by summing the individual axle loads stored in thememory at block 416. The processor then displays the individual axleloads and the total vehicle load (block 428). In one embodiment, theloads are displayed on a screen of the input/output unit of thecontroller and printed onto a receipt using a printer, while in otherembodiments the loads are ether displayed on the screen or printed ontoa receipt. In some embodiments, the axle and total loads are stored inthe memory, while in other embodiments the axle and total loads aretransmitted to an external device, such as a computer or a smartphone,via, for example, a serial, Ethernet, Wi-Fi, or Bluetooth connection. Infurther embodiments, the axle and load data is stored in “the cloud” andprinted remotely of the axle scale. In some embodiments, the processoris further configured to recall a vehicle load from a previous pass overthe scale by the same vehicle, and determine the net load of the vehicleby subtracting the stored load in the previous pass from the total loaddetermined at block 424.

Advantageously, the axle scale 100 can be manufactured at a locationremote from the installation site and can be installed as aprefabricated axle scale. A process diagram of a method 500 ofmanufacturing such a weighing system is depicted in FIG. 15. The processbegins with the forming of a base having a scale opening and a pluralityof load cell openings opening laterally to the scale opening (block504). In one embodiment, the base is formed by assembling a steel baseframe to define the scale opening and the load cell openings and thencasting concrete in the shape of a rectangular prism around the steelbase frame.

A support member pair is provided for each of the load cell openings(block 508). In one embodiment, the support member pair is providedduring the forming of the base by, for example, welding the supportmember pairs onto the base frame as the base frame is being assembled.In another embodiment, the support member pairs are provided afterformation of the base.

The process continues with the formation of a platform structure (block512). In some embodiments, the platform structure is formed afterformation of the base, while in other embodiments, the platformstructure is formed before or during formation of the base. In oneembodiment, the platform structure is formed by assembling a platformframe of, for example, webbed steel beams in the shape of a rectangle,and casting concrete within the platform frame to form a planarhorizontal top surface of the platform structure.

A lower portion of each of a plurality of load cell assemblies ismounted pivotably to the platform structure, extending outwardly fromthe platform structure (block 516). In one embodiment, the load cellassemblies are attached to the steel beams of the platform frame with aconnection plate, and a load pin extends between the connection platesthrough the lower portion of the load cell assembly.

Finally, an upper portion of each of the plurality of load cellassemblies are supported in a respective one of the support member pairsat their neutral (i.e. unloaded) position (block 520). In oneembodiment, the load cell assemblies are each connected to a fulcrumpin, which engages a saddle groove in each of the support members or therespective support member pair as the platform structure is lowered intothe platform opening in the base. The flexure cover plates 189 can thenbe removed, if present, and the bolts 179 used to fixedly bolt theflexures 177 to the flexure bases 149. The bolts in one embodiment areremovable to allow for disassembly of the system. The flexure coverplates 189 are then installed.

A process diagram of a method 600 of installing a weighing system isdepicted in FIG. 16. The process begins with the preparation of a scalesite (block 604). In one embodiment, the site includes a flat approachat least twice the length of the vehicles that will be weighed by theweighing system, though other embodiments include an approach that islonger or shorter than two vehicle lengths. The preparation of the scalesite additionally includes excavating a location in which to install thescale and laying two layers of stone compacted flat and leveled.

After preparation of the site, the pre-fabricated weighing system islowered into the excavated site (block 608). The area surrounding theweighing system is then leveled to the same height as the weighingsystem (block 612). In some embodiments, a concrete approach is cast oneither side of the weighing system, while in other embodiments a gravel,dirt, or asphalt approach is used.

The scale controller is then installed proximate to the scale site(block 616). The scale controller is connected to the load cells (block620) and a power source. The power source in some embodiments includesone or more of a wired power connection, a battery, and a solar cell. Inone embodiment, the weighing system includes a conduit extending throughthe weighing system to route the cables from the load cells forconnection to the scale controller.

The pre-fabricated weighing system is further configured such that theweighing system is semi-portable. The weighing system is removed bydisconnecting the controller from the load cells and excavating the areasurrounding the scale. The weighing system is then removed from the siteand can be transported to another desired site for installation.

FIG. 17 illustrates a method 700 for maintaining a weighing system. Alifting device, for example a forklift, a backhoe, or a crane, isattached to anchor points on a platform structure of the weighingapparatus (block 704). In some embodiments, a quick-disconnect cableconnecting the load cells to the controller is disconnected from within,for example, an opening located in the center of the platform structure.The platform structure is then lifted out of a platform opening in thebase (block 708). The weighing system is configured such that theplatform structure merely rests in the base, and is not positivelyattached to the base. As such, the only force the lifting apparatus mustovercome to remove the platform structure is the weight of the platformstructure and any attached components. Furthermore, the load cells ofthe weighing system are positively attached only to the platformstructure, and are configured only to rest on the base. Thus, the loadcells need not be decoupled from the base or the platform structurebefore removal of the platform structure.

Once the platform structure has been removed from the platform opening,any desired maintenance operations are performed in the platform opening(block 712). In some embodiments, the maintenance operations includeremoval of dirt and debris accumulated underneath the platform structureduring normal operation of the weighing apparatus. The platformstructure is then lowered back into the platform opening (block 716).Advantageously, since the load cells are not positively connected to thebase, no additional attachment of the load cells, with the exception ofreconnecting the quick-disconnect cable, is necessary to reinstall theplatform structure and the load cells need not be recalibrated afterreinstallation of the platform structure. The lifting device is thendetached from the anchor points of the platform structure (block 720)and the maintenance process is complete.

Although the disclosed weighing system is described with reference to anaxle scale for a vehicle, the reader should appreciate that the scaledescribed herein can also be used for weighing other types of loads. Forexample, the scale is suitable for weighing moving objects on amanufacturing conveyor system or on an assembly line.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe disclosure are desired to be protected.

1. A weighing system, comprising: a base; a platform structure movablewith respect to the base and including a planar top surface defining ahorizontal plane; at least one flexure fixedly attached to the platformand the base, the at least one flexure configured to inhibit movement ofthe platform structure along the horizontal plane relative to the base;and a plurality of load cell assemblies, each of the plurality of loadcell assemblies including an upper portion pivotably supported by thebase through a first pivot assembly and a lower portion pivotablysupporting the platform structure through a second pivot assembly, eachof the plurality of load cell assemblies positioned such that when theupper portion of each of the plurality of load cell assemblies isprojected onto the plane and the planar top surface is projected ontothe plane, each of the projected upper portions is located outwardly ofthe projected planar top surface, wherein an axis of rotation of thefirst pivot assembly is parallel to an axis of rotation of the secondpivot assembly.
 2. The weighing system of claim 1, wherein: the platformstructure includes a frame with a first beam; and the at least oneflexure is fixedly attached to the first beam.
 3. The weighing system ofclaim 2, wherein: the frame includes a second beam spaced apart from thefirst beam; and the at least one flexure is fixedly attached to thesecond beam.
 4. The weighing system of claim 3, wherein: the platformincludes at least one flexure opening; the at least one flexure isfixedly attached to the base by at least one bolt; and the at least onebolt is accessible through the planar top surface through the at leastone flexure opening.
 5. The weighing system of claim 4, wherein the atleast one flexure comprises a plurality of flexures.
 6. The weighingsystem of claim 5, wherein each of the plurality of flexures ispositioned such that as a vehicle passes over the platform structureduring a weighing operation, each of a plurality of wheels of thevehicle passes directly above a respective one of the plurality offlexures.
 7. A method of providing a weighing apparatus comprising:forming a base having a scale opening, and a plurality of load cellopenings opening laterally to the scale opening; providing a supportmember pair for each of the load cell openings; forming a platformstructure; pivotably mounting a lower portion of each of a plurality ofload cell assemblies to the platform structure through a first pivotassembly; fixedly connecting at least one flexure to the platformstructure; supporting an upper portion of each of a plurality of loadcell assemblies with a respective one of the support member pairsthrough a second pivot assembly, wherein an axis of rotation of thefirst pivot assembly is parallel to an axis of rotation of the secondpivot assembly; and fixedly connecting the at least one flexure to thebase after supporting the upper portion of each of the plurality of loadcell assemblies.
 8. The method of claim 7, wherein fixedly connecting atleast one flexure to the platform structure comprises: fixedlyconnecting the at least one flexure to a first beam of a frame of theplatform structure.
 9. The method of claim 8, wherein fixedly connectingat least one flexure to the platform structure further comprises:fixedly connecting the at least one flexure to a second beam of theframe of the platform structure, the second beam spaced apart from thefirst beam.
 10. The method of claim 9, wherein fixedly connecting the atleast one flexure to the base comprises: inserting a bolt at leastpartially through the at least one flexure and into a bolt hole in thebase; accessing the bolt through a top surface of the platformstructure; and tightening the accessed bolt.
 11. The method of claim 10,wherein fixedly connecting at least one flexure to the platformstructure comprises: positioning each of a plurality of flexures suchthat as a vehicle passes over the platform structure during a weighingoperation, each of a plurality of wheels of the vehicle passes directlyabove a respective one of the plurality of flexures; and fixedlyconnecting each of the positioned plurality of flexures to the platformstructure.
 12. A method of weighing a vehicle comprising: moving atleast a portion of a vehicle onto a platform structure including aplanar top surface defining a horizontal plane by movement of a portionof the vehicle past at least two of a plurality of load cell assembliesand then onto a platform structure, wherein the platform structure issupported by a plurality of load cell assemblies through a plurality offirst load transfer areas, and each of the plurality of load cellassemblies is supported by a base through a respective one of aplurality of first load transfer areas, each of the first load transferareas located farther from the horizontal plane than each of the secondload transfer areas; inhibiting movement of the platform structure alongthe horizontal plane using at least one flexure fixedly attached to theplatform structure and the base; forcing each of the second loadtransfer areas from a neutral position directly away from the horizontalplane by moving the at least a portion of the vehicle onto the platformstructure; and determining a weight based upon signals generated by theplurality of load cell assemblies.
 13. The method of claim 12, whereininhibiting movement of the platform structure along the horizontal planecomprises: inhibiting movement of the platform structure along thehorizontal plane using at least one flexure fixedly attached a firstbeam of a frame of the platform structure.
 14. The method of claim 13,wherein inhibiting movement of the platform structure along thehorizontal plane further comprises: inhibiting movement of the platformstructure along the horizontal plane using at least one flexure fixedlyattached to a second beam of the frame of the platform structure, thesecond beam spaced apart from the first beam.
 15. The method of claim14, wherein moving at least a portion of a vehicle onto a platformstructure comprises: moving each of a plurality of wheels of the vehicledirectly above a respective one of the plurality of flexures.